Add tests for user_group_distinguished_names()

In https://github.com/stackabletech/opa-operator/pull/622#top we added an Active Directory backend to the user info fetcher.

As part of this, there was fairly extensive code to convert between some weird representations which AD chose for userids and groupids.

In order to not block the release with this we decided to punt on adding unit tests (hopefully, worst case: integration tests) for this later.

We should try and get this done fairly soon after 24.11.

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• Describe the use-case, as far is possible. For instance, using the pattern "As a XXXX, I would like XXXX to be able to do XXXX" helps to identify the feature as well as the problem it is intended to address.
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• Indicate if there is a known work-around until such time as the issue has been implemented.

Commencez par le code d’implémentation et de conversion ajouté dans pull request 622, en particulier le chemin user_group_distinguished_names(). Ajoutez des tests unitaires ou, si nécessaire, des tests d’intégration couvrant les représentations des ID utilisateur et groupe d’Active Directory ; le travail est terminé lorsque le comportement de conversion est testé sans bloquer le release.